I have a 2005 Z71 tahoe with the towing package and a 7 pin connector. I have to pick up a trailer this week that has electric brakes. I have never towed with my truck before. Stupid question here but to get the trailer breaks to operate, do I have to install a brake controler or does my truck already have one with the towing package? I am assuming I must first purchase and install a brake controller right?